In high volume fluid transfer operations, such as hydraulic fracturing to produce natural gas from shale, large amounts of water are required to be stored and managed. For instance, several millions of gallons of water can be required for hydraulic fracturing at a single well. Water is stored on site near the well, and is blended with a proppant material such as sand to form a slurry which is injected into the well and into the shale formation, thus opening the shale formation to allow natural gas or oil to flow. Water is returned from the shale through the well to the surface in the form of flowback water. This water can then be treated to remove contaminants and reused at additional well sites.
A limited number of options are currently available to manage water storage at a well site. According to one currently available option, many 500 barrel (bbl) storage tanks are rented for the duration of hydraulic fracturing and flowback operations at a particular well. The use of such tanks results in very large well pad area requirements, which is undesirable from land use, environmental and aesthetic perspectives. Such tanks are furthermore difficult to clean and expensive to rent.
A second currently available option for managing water storage in hydraulic fracturing operations is the use of large deconstructable water storage tanks, such as 25,000 bbl deconstructable water storage tanks. One such tank 10 having an interior 18 for storing hydraulic fracturing fluid 12 is illustrated in FIG. 1. Such tanks are typically 15 foot (4.6 m) high structures made up of steel panels 16. The tanks are typically lined with a polyvinyl chloride (PVC) or polypropylene (PP) bag or liner. These are expensive to rent and also result in very large well pad requirements. The tank may rest on a cement pad 14 in the ground 1. The liners can present difficulties for disposal, and the liners can also be inadvertently sucked into pumps that remove water from the tank during operation. Such tanks do not meet American Water Works Association (AWWA) seismic code and must be built at lower heights to meet 100 mph wind code. Furthermore, it can be difficult to place this type of tank with secondary water containment.
A third currently available option used to manage water storage in hydraulic fracturing operations is illustrated in FIG. 2. Open ponds or pits 20 such as 25,000 bbl pits are lined with PVC or PP liners 22. Such pits have a maximum depth of 15 feet (4.6 m) indicated at 92, and have slope requirements indicated at 80 of no more than 3:1 (horizontal:vertical). Such pits therefore result in large well pad requirements. As indicated by 90, 6 typical tank widths 10 can fit within one such pond 20. Such pits typically require fencing or other barriers to prevent unauthorized entry. Double liners can be used to reduce the likelihood of leakage, but this adds to the cost. Furthermore, open pits for flowback water may be aesthetically unappealing.
The need remains for improved water storage management in high volume fluid transfer operations such as hydraulic fracturing. It would be desirable to have a system which would not require a large well pad area and which could be easily assembled, disassembled and transported to multiple well sites. It would further be desirable for the system to meet American Water Works Association (AWWA) specifications, seismic code, wind load code and increased water storage.